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What are swirl flaps?

Swirl flaps are designed to create swirl or tumble of the air to aid better combustion under light load where soot levels tend to be dominant because of the lack of air, they are also there to help with driveability in low load conditions, they are controlled by a vacuum or solenoid actuator and are closed during light-load operations such as when idling at traffic lights, changing gear and deceleration to maximise combustion efficiency, fuel economy and emissions performance. The flaps are fully open during higher load conditions to maximise volumetric efficiency and power output.

The swirl flaps are a poor design, they are prone to failure. When the swirl flap breaks, the debris falls into the engine, either sticking in the valve port and jamming it open, causing the piston to collide with the valve, or falls into the cylinder itself causing the piston and head to become damaged.

What is the solution?

BMW introduced an updated manifold in 2004 to address this problem, the spindle of the valve is thicker and stronger, this design is also prone to failure, another option is to purchase a new manifold and install it, however you will still havethe potential for the same problem to occur.
The easiest and cheapest solution is to use our custom manufactured blanking plates, the blanks will fit in place of the current mechanism, there is no modification required! The plates are manufactured to the highest possible standards from aluminium.

The car will function the same without the flaps, the flaps are there for emissions purposes, however the car will remain within guidelines and you will not notice a performance change!